Method for forming semiconductor fine-pitch pattern

1. A method for forming a fine-pitch pattern on a semiconductor substrate, comprising:

patterning the semiconductor substrate to form a plurality of fine lines;

forming a thermal oxide layer on the fine lines;

polishing the thermal oxide layer to expose a top surface of the fine lines; etching the fine lines using the thermal oxide layer as a mask to expose first portions of the semiconductor substrate;

etching a central bottom portion of the thermal oxide layer to expose second portions of the semiconductor substrate; and

etching the semiconductor substrate using the etched thermal oxide layer as a mask.

2. The method of claim 1 , wherein patterning the semiconductor substrate comprises:

forming a patterned nitride layer on the semiconductor substrate;

etching the semiconductor substrate using the nitride layer as a mask to form the fine lines; and

removing the nitride layer.

3. The method of claim 1 , wherein forming the thermal oxide layer on the fine lines comprises oxidizing the semiconductor substrate.

4. The method of claim 3 , wherein oxidizing the semiconductor substrate reduces a size of the fine lines of the semiconductor substrate by about 35% to about 55%.

5. The method of claim 3 , wherein oxidizing the semiconductor substrate comprises oxidizing the semiconductor substrate in a wet atmosphere.

6. The method of claim 1 , wherein etching the semiconductor substrate or etching the thermal oxide layer comprises performing a reactive ion etching (RIE) process.

7. The method of claim 1 , wherein etching the fine lines comprises removing a portion of the fine lines using an fluorine (F) based solution in accordance with an etching ratio of the thermal oxide layer to the semiconductor substrate.

8. The method of claim 7 , wherein the F based solution comprises a fluorinated ethylene propylene (FEP) solution.

9. The method of claim 7 , wherein the etching ratio is about 10:1 to about 20:1.

10. The method of claim 8 , wherein the FEP solution is formed by combining a plurality of ethylene (—CH 2 CH 2 —) units and a plurality of propylene (—CH 2 CH 2 CH 2 —) units and replacing a plurality of hydrogen components with a plurality of fluorine components.

11. The method of claim 2 , wherein forming the patterned nitride layer comprises:

forming a nitride layer on the semiconductor substrate;

forming a patterning auxiliary layer on the nitride layer;

forming a reflection preventing layer on the patterning auxiliary layer;

forming a photoresist layer on the reflection preventing layer;

patterning the photoresist layer to expose portions of reflection preventing layer;

patterning the reflection preventing layer, the patterning auxiliary layer, and the nitride layer using the patterned photoresist layer as a mask; and

removing remaining portions of the reflection preventing layer, the photoresist layer, and the patterning auxiliary layer.

12. The method of claim 11 , wherein removing the remaining portions of the reflection preventing layer, the photoresist layer, and the patterning auxiliary layer comprises using a wet cleaning process.

13. The method of claim 11 , wherein the patterning auxiliary layer comprises a tetraethyl orthosilicate (TEOS) layer having a thickness of at least 1,000 Å.

14. The method of claim 11 , wherein forming the nitride layer comprises forming the nitride layer using a low pressure chemical vapor deposition (LPCVD) process.